Effects of arc bubble behaviors and characteristics on droplet transfer in underwater wet welding using in-situ imaging method

The effects of arc bubble behaviors and characteristics on droplet transfer are observed with an in-situ X-ray imaging method. The changes in the force acting on the droplet arc analyzed at three distinct stages of arc bubble in one life cycle. The maximum gas flow drag force acting on the droplet exists in the moment that bubble just contacts the droplet. The deviation angle between droplet and wire axis increases with the bubble expansion rate, which increases the probability of welding spatter, and then reduces welding stability. The deviation angle of droplet is reduced by limiting the expansion of arc bubbles at a certain hydrostatic pressure. A new kind of arc bubble constraint device is designed and applied to limit the free expansion and floatation of arc bubble, which improves the metal transfer stability and the weld appearance. (C) 2019 The Authors. Published by Elsevier Ltd.